1. Technical Field
The present invention relates to a high speed laser package and, more particularly, to a package which utilizes a hybrid metallic-ceramic arrangement to provide a laser connection with the bandwidth required for high speed operation.
2. Description of the Prior Art
In the field of lightwave communications, there is a constant demand to increase the speed at which laser-based transmitters operate. Less than five years ago, most transmitters operated at speeds of approximately 560 Mb/s. In the past few years, the speed has continued to increase to 880 Mb/s, 1 Gb/s and beyond. The push to multi-gigabit operation has stressed the performance of conventional laser packaging. In particular, problems are created in coupling the input data signal to the laser, since conventional electrical contacts develop an extremely large parasitic series inductance. As is well-known in the art, the inductance functions to decrease the bandwidth of the connection and limits the data rate of the signal applied thereto. Analog, as well as digital applications exist where it is desired to provide a multi-GHz, high frequency interconnection. In general, the multi-gigabit and multi-GHz applications will be referred to hereinafter as "high speed" applications. Borrowing from microwave technology, a coaxial connection may be utilized in place of the conventional electrical connection to reduce the parasitic inductance. U.S. Pat. No. 4,309,717, issued Jan. 5, 1982, discloses one such coaxial input arrangement. As disclosed, a conventional coaxial line is inserted through a standard metal laser package, hermetically sealed in place, and connected to the laser. Although this arrangement solves the problem associated with standard electrical connections at high speeds, the package itself is bulky, expensive and relatively difficult to manufacture.
An improved laser packaging arrangement which advantageously utilizes a multilayer ceramic (MLC) structure to provide the interconnection between the signal source and the laser is disclosed in U.S. Pat. No. 4,873,566, issued on Oct. 10, 1989. In this arrangement, a multilayer microwave transmission line, formed within the wall of a ceramic package, is utilize to provide the high speed interconnection. Such a package is capable of using any set of leads to form the transmission line and, indeed, more than one transmission line may be formed as part of a single package. The use of such a ceramic package including a microwave transmission structure has been found to allow operation at data rates in excess of 1 Gb/s. However, many transmitter and/or system designs require the use of the more conventional metallic package design (in particular, its common "butterfly" configuration--the term "butterfly" referring to an arrangement where the leads exit symmetrically through the package sidewalls).
Therefore, a need remains in the art for a means of providing a connection between a signal source and a packaged laser which provides the bandwidth required to support high speed operation, while remaining compatible with existing packaging and applications technology.